Periods for 1 day only. 54cc plz guide!

Hi..Am 5'5" and 45 kg..My periods were always regular..And they were always for 2-3 days wherein 1st day used to be normal whereas rest of the days it used to be light...From last 3-4 cycles my periods are for 1 day only and the cramps I used to feel earlier were also different from the ones am facing now, blood colour is on darker side plus the flow is extremely less..I had some tests done on 23 Jan (period was on 8 Jan), wherein thyroid, sugar, blood reports all were normal..FSH is 4.32 and LH is 8.80... Ultrasound reports shows endometrial echo is seen in midline and measures 7.1mm in thickness, bilateral ovaries show few small predominantly peripherally arranged follicles in a polycystic pattern. Right ovary measures 2.8cmx2.0cmx2.7cm ovarian volume is 8.45cc Left ovary measures 2.5cmx1.9cmx2.8cm ovarian volume is 7.54cc Plz guide